1. Field of the Invention
The present invention relates to an enhanced movement detection arrangement, and in particular, to a security arrangement that detects unauthorized movement of an electronic device, such as a computer.
2. Background Information
Computers, in general, have in recent years increased in power and decreased in size. For example, computers have now reached a size where the functionality of a full-size computer system can now be performed by so-called laptop or notebook computers, which are typically small, light weight systems. Moreover, portable electronic organizers, known as personal digital assistants (also known as PDAs), are becoming increasingly popular. Personal digital assistants typically have both a size and weight that are even less than that of even the smallest laptop or notebook computers. For example, a typical personal digital assistant may have a height of only about 4.5 inches, and a weight of only about 6 ounces, so that it may be easily carried in a pocket or purse of a user.
A driving force in the configuration of laptop computers, notebook computers, and personal digital assistants (hereinafter, also portable and/or personal computer), is to make them even smaller and lighter, and thus easier to transport. As laptops and notebook computers, and personal digital assistants, become smaller and lighter, they are also made easier to conceal. The fact that these devices are easy to transport and conceal has led to an increase in the amount of theft of such systems.
Laptop and notebook computers, and personal digital assistants, are generally stolen by people who may see one lying unattended, and who simply pick up the computer and place it in a briefcase, for example. Alternatively, the device may be stolen with no effort being taken to conceal the theft. As a result, both display models, (e.g., those devices placed on display in stores), and personally-owned computers, are being stolen at an alarming rate.
To help prevent the theft of such systems, various security systems have been proposed. For example, it is known to anchor the portable computer to a desk or table. Although this may provide an adequate anti-theft deterrent, the anchors used tend to be unsightly and cumbersome. Moreover, the anchors are typically not fully portable, which may prevent the portable computer from being secured outside of the normal work environment.
It is also known to employ sensors that detect motion, and which may be integrated into the micro-processor of the portable computer. For example, mercury switches have been used which detect a tilting of the portable computer. If the portable computer is tilted by unauthorized movement, an alarm, for example, can be activated. However, the mercury within a mercury switch is highly toxic. As such, the use of such switches raises environmental and safety concerns which must be addressed by a manufacturer. Thus, there is a need for a sensor that does not require mercury for its activation.
Moreover, such switches will only work properly if the switch is in a horizontal position. Thus, the use of a mercury switch will prevent the portable computer from being used on an inclined surface, or at an angle to the horizontal. This is disadvantageous, since laptop computers, as the name implies, may be operated while on the lap of a user. Unless the lap of the user maintains the computer in a horizontal position, a false alarm may result. Therefore, there is a need for a sensor that will allow the computer to be operated beyond a horizontal position.
Further, a mercury switch can be defeated in a relatively easy manner by keeping the portable computer in its horizontal position during its theft. As long as the portable computer is kept horizontal, the mercury switch will not be activated, and an alarm will not sound.
It is also know to provide sensors that detect movement in a vertical direction. For example, a typical sensor may have a switch body, and a vertically-displaceable plunger disposed within the switch body. A spring may be provided to urge the plunger in a downward direction. The sensor is typically disposed on a base of a computer, so that an outwardly-disposed end of the plunger is contactable with a surface of a table, for example. As long as the computer remains on the table, the plunger is retracted and maintained in a predetermined location, and the sensor remains inactivated. However, if the computer is lifted off the table, the spring urges the plunger downward, thus allowing the sensor to assume an activated state.
Typically, the end of the plunger is configured to have a convex (rounded) surface, so as to simulate a foot of the computer. However, this configuration allows the sensor to be defeated merely by sliding a relatively rigid article, such as a piece of cardboard, under the end of the plunger. Thereafter, both the rigid article and the computer can be lifted off the supporting surface (such as the table) without activating the associated alarm system. Alternatively, the computer can be simply slid to the edge of the table, to allow the plunger to be grasped and held in its retracted state. Thus, there is a need for a sensor that is difficult to defeat, and that will detect both sliding and lifting motion of the portable computer.
As noted above, the known sensors may be integrated into, for example, electrically coupled with, the micro-processor of the portable computer. Thus, a keypad of the computer can be used to enter a code, for example, to activate and/or deactivate the sensor. If the correct code is entered, then the sensor may be moved without initiating an alarm condition.
Further, it is also known to utilize the micro-processor to render data stored in a portable computer useless, by erasing the data contained therein and/or by rendering the portable computer inoperable, depending on whether the sensor has been activated or not. However, this arrangement is only intended to prevent the unauthorized use of the system, rather than preventing the theft of the system. As will be appreciated, the knowledge that a stolen portable computer can not be used by the thief, will provide little relief to the authorized user or owner of the portable computer.